Rep. Peter J. Roskam (R-Ill.) is in the fight of his political life against Sean Casten. A clean-energy entrepreneur, Casten has reserved $4.6 million worth of ads, well ahead of Roskam’s $2 million in ads. (J. Scott Applewhite/AP)

One by one, Democrats running for the House have released jaw-dropping figures the past week: First-time candidates raising $2.7 million in New Jersey, $3.5 million in California’s Central Valley and more than $3.6 million in northern Kentucky.

That’s just the previous three months, gaining steam on a fundraising surge that began last year. But the more eye-popping way to examine the Democratic cash is through the combined look at what that money does for their candidates.

In terms of television and radio advertising, Democratic candidates are expecting to spend almost $50 million more than their Republican counterparts in about 70 top House races, according to a spreadsheet of ad reservations across the country.

That spreadsheet, known as the “competitive summary” by insiders, was maintained by Republican operatives and provided to The Washington Post by GOP strategists.

They requested anonymity to discuss their growing fear that Democratic candidates will overwhelm Republicans in the home stretch of the midterm elections, and the overall outlines of the spending trends were confirmed by other Republican and Democratic operatives.

To be sure, Republicans have a committed group of mega-donors who have seeded outside conservative groups with seven- and eight-figure checks that have helped make up some of the difference. The two biggest GOP spenders, the National Republican Congressional Committee and its super PAC ally, the Congressional Leadership Fund, have reserved almost $140 million in ads from the summer through Election Day, well ahead of the $105 million reserved so far by their Democratic counterparts.

And there is still time for more mega-donors to arrive and provide CLF and other super PACs with dollars that will level the playing field.

But, overall, Democrats have an edge financially in the final weeks of the season, and that edge could be decisive because candidates get better advertising rates than party committees and super PACs.

Corry Bliss, the CLF executive director, sent a memo to donors Tuesday that highlighted signs of growing enthusiasm among conservative activists in the wake of the high-profile clash over the Senate’s confirmation of Justice Brett M. Kavanaugh to the Supreme Court.

Some 60 Democrats raised more than $1 million in the third quarter, a big number for House races, but 30 of those raised more than $2 million and eight raised more than $3 million — those are levels usually reached by statewide candidates for Senate or governor.

Think of it as the “Conor Lamb Effect.”

Rep. Lamb (D) in March won a long-shot race for a special election in southwestern Pennsylvania, a conservative district that went heavily for President Trump two years ago.

Lamb, a former federal prosecutor and Marine, far outraised his lackluster Republican opponent and, despite a bailout effort by GOP outside groups, he was able to run about as many ads as all Republican entities combined.

After Lamb’s victory, Republicans tried to warn their incumbents that they needed to raise money on their own and not wait for outside help. “It’s been clear to everyone that candidate dollars mattered,” said Matt Gorman, spokesman for the NRCC.

Officials with the Democratic Congressional Campaign Committee beefed up their digital teams last year to connect them with campaigns like Lamb’s, building the online infrastructure necessary to raise huge sums from liberal donors looking for ways to support anti-Trump candidates.

“Candidate ads are more effective at introducing candidates, carrying the positive message and rebutting attacks directly to camera,” said Meredith Kelly, spokeswoman for the DCCC.

That is a polite way of another well-understood fact: Political consultants put in far more effort to produce quality ads for the candidates, as opposed to the cookie-cutter ads they often produce for super PACs.

The Lamb phenomenon is now replicating itself in dozens of races, as liberal activists have used online portals such as ActBlue to pour donations into the top targeted districts.

First-time candidates like Mikie Sherrill in New Jersey and Josh Harder in California dwarfed their GOP opponents in fundraising. Sherrill, a former Navy helicopter pilot and federal prosecutor, is now favored to win a seat held by Republicans for more than 30 years.

Harder, a venture capitalist, is locked in a toss-up race with Rep. Jeff Denham, a moderate Republican familiar with winning tough races in the Central Valley.

Denham took this race seriously and had already raised $3.5 million by June 30.

But Harder hauled in that much just from July through September, and he is now poised to have a large advantage in the closing weeks. His campaign reserved $4.1 million in advertising in the final months of the season, almost double the $2.1 million reserved by Denham’s campaign, according to the Republican “competitive” spreadsheet of races.

The two primary GOP groups, NRCC and CLF, have reserved $4.8 million in ads in that district, compared with $3.7 million from the DCCC and its super PAC ally, House Majority PAC.

The same dynamic is taking place outside Chicago, where veteran Rep. Peter J. Roskam (R-Ill.) is in the fight of his life against Sean Casten. A clean-energy entrepreneur, Casten has reserved $4.6 million worth of ads, well ahead of Roskam’s $2 million in ads.

Democrats have also benefited from liberal activists pouring donations into the DCCC. Donors are limited to checks of $33,900 to such a party committee, but online fundraising has led to an outpouring of small-dollar donors who have provided the DCCC a significant advantage over the NRCC.

The Democratic committee has, so far, reserved $63.5 million in ads, compared with $46.8 million for the Republican committee.

This energy among liberal donors has forced Republicans into hard choices about where to spend their dollars. At the moment, the NRCC has only a small shared ad with Roskam, and no money reserved on behalf of the former member of Republican leadership from its roughly $50 million fund for independent expenditure ads.

The NRCC has so far entirely abandoned a trio of Republican districts in Southern California considered toss-ups: the seats of Reps. Steve Knight and Dana Rohrabacher, as well as the seat of retiring Rep. Edward R. Royce.

Instead, the super PAC is the only one playing defense against a trio of Democratic candidates who are swamping the Republican candidates in fundraising.

“We knew Republicans were going to have a huge resource advantage and candidate money was necessary to combat that discrepancy,” Kelly said.

Paul KanePaul Kane is The Washington Post's senior congressional correspondent and columnist. His column about the 115th Congress, @PKCapitol, appears throughout the week and on Sundays. He joined The Post in 2007. Follow